1. Field of the Invention
The present invention relates to a broadband wireless communication system. More particularly, the present invention relates to an apparatus and method for transmitting/receiving system information in a broadband wireless communication system.
2. Description of the Related Art
At present, a mobile communication system is evolving beyond voice-centric communication to provide a variety of services such as broadcasting, a multimedia video, a multimedia message, etc. Examples of this next-generation communication system are an Institute of Electrical and Electronics Engineers (IEEE) 802.16e system, a 3-Generation Partnership Project (3GPP) Long Term Evolution (LTE) system that is now under standardization, an IEEE 802.20 Ultra Mobile Broadband (UMB) system, an IEEE 802.16m system, and the like.
In order to support a high data transmission speed in the mobile communication system, various transmission techniques such as the use of a multiple antenna system, Hybrid Auto Repeat reQuest (HARQ), Adaptive Modulation and Coding (AMC), and the like are being introduced. In order for these transmission techniques to be managed, a Base Station (BS) has to transmit a significant amount of system information to a plurality of user Mobile Stations (MSs). The system information includes network and cell information that a user MS must be aware of to perform mobile communication within a cell. For example, the information may include bandwidth information of the cell, configuration information of a physical channel, information of a parameter, etc. of an upper layer, etc., and information of various transmission techniques supported in the cell, for example, number of transmit antennas, information of a multiple antenna, HARQ related information, modulation scheme information, etc.
According to the IEEE 802.16m standard, which is one of the wireless communication standards, system information is transmitted in a form of a Primary-Super Frame Header (P-SFH) and a Secondary-Super Frame Header (S-SFH). The S-SFH is divided into a SubPacket1 (SP1), an SP2, and an SP3. Transmission periods of the SP1, the SP2, and the SP3 can be different from each other. The P-SFH includes information informing if the S-SFH is transmitted in the same frame in which SP is transmitted, and its size. Also, the P-SFH represents a change of the system information using an S-SFH change count and an S-SFH SP change bitmap. The P-SFH informs which SP is transmitted in the same frame using an S-SFH scheduling information bitmap.
The S-SFH change count is mapped to transmitted SPs. For example, in case that the S-SFH change count is equal to ‘N’, transmitted SP1, SP2, and SP3 include system parameters of a state of ‘S-SFH Change Count=N’. Accordingly, a change of the S-SFH change count means that at least one of the SPs of the S-SFH has been updated. The S-SFH SP change bitmap represents which SP has been changed. Also, each SPx includes an offset parameter of two bits indicating an offset of a superframe in which the use of a changed SP starts, and indicates when a new configuration changed through the offset parameter is applied. Accordingly, after receiving a new SPx, the MS applies new parameters in the superframe indicated by the offset parameter within the SPx.
The S-SFH change count and the S-SFH SP change bitmap included in the P-SFH indicate that the system information has been updated and which SP has been updated. However, although the MS recognizes the update of the system information and the updated SPx by receiving the P-SFH, in a case in which the MS fails to receive the updated SPx due to channel degradation, an operation state of a sleep mode, etc., the MS must stop communication because it is not aware of a time point of application of the updated SPx. Accordingly, the MS cannot perform communication until successfully decoding the SPx. Thus, there is a need for an alternative for, although failing to receive an updated SPx, enabling an MS to perform communication until before application of updated system information, by recognizing a time point of application of the updated SPx.